Conventional endoscopes are often supplied with illumination from an external light source. The light sources are generally coupled to the endoscope by means of a detachable waveguide or fiber optic light cable.
Such light sources generally include high intensity lamps, such as an incandescent or arc lamps. However, one issue with the use of such lamps is that their intensity cannot effectively be controlled by conventional means, such as reducing the power to the lamp through an electronic dimmer control. Instead, high intensity lamps are generally operated at full power and an alternate system is provided to reduce the intensity of the light transmitted to an endoscope for illuminating a site.
Another issue with high intensity lamps is that they produce a high amount of infrared energy, which if not properly reduced can cause damage. For example, light from a high intensity lamp can burn operating drapes, a patient's skin, or clothing.
Still further, as a high intensity lamp ages, the intensity of the lamp reduces and the color temperature drifts. For example, once a lamp has aged to the point where the output intensity is approximately 20-25% of a new lamp, the color temperature of the lamp output begins to drift. The color temperature drift can be so dramatic that an endoscopic camera system used with the light source may no longer correctly white balance the image. Thus, all images acquired by the camera will be off color, which can have tragic results if a surgeon using the light source makes an incorrect diagnosis based upon inaccurate tissue color and/or appearance.
Therefore, when using high intensity lamps in endoscopic light sources, it is desirable that both the intensity and infrared energy of the light transmitted to the endoscope is attenuated. It is also desirable that the color temperature of the lamp is monitored.
The reduction of the transmitted intensity of a lamp using a mechanical attenuator is effective for use with endoscopic light sources. Such systems are disclosed in U.S. Pat. No. 5,006,965. However, this and other known devices do not effectively control the light output intensity as a lamp degrades or inform a user when a lamp needs to be replaced. Such devices also do not inform a user when the color temperature of the lamp drifts. Still further, such devices do not inform a user if the infrared energy emitted by the system is too high. Thus, with such devices disclosed in the prior art, it is difficult for a user to maintain a consistent light output intensity, for a user to know when the color temperature of the light source has drifted and for a user to determine if too much infrared energy is being output.
It is therefore desired to provide an improved endoscopic light source that automatically detects the intensity of a lamp and reduces the intensity to a predetermined level. It is further desired, that the system will inform a user when the lamp's intensity falls below a predetermined level, the color temperature is no longer acceptable and if the infrared energy is above a predetermined value.